Trimmer line with inner and outer cutting portions

ABSTRACT

A cutting attachment for use with a vegetation cutting device. The cutting attachment has a body with a generally planar coupling portion and a central axis of rotation. In one embodiment, the body further includes a conical central wall portion extending radially outwardly and in a first direction from the coupling portion and the axis and a circular outer wall portion adjoining the central wall portion and extending generally radially outwardly therefrom. The central wall portion defines a conically-shaped self-cleaning inner cavity disposed symmetrically about the axis. The outer wall portion has a generally smooth outer surface which serves as a skid plate. An outer self-cleaning cavity is formed by an outer surface of the central wall portion and an inner surface of the outer wall portion. A coupling assembly, which can include an adapter having first and second clamping elements, is carried by the coupling portion for coupling the body to the cutting device to cause rotation about the axis. A plurality of spaced apart radially extending cutting elements, in the form of cutting blades and/or cutting strings, are carried by the body. Cutting blades are provided with aerodynamic configurations, serrated edges, inner and outer cutting edges and arms for securing the blades to the cutting attachment which permit longitudinal movement of the cutting blade with respect to the cutting attachment. Cutting strings are provided with inner and outer cutting portions, grooves for reducing fraying and a spiraled configuration.

This is a continuation of application Ser. No. 08/487,194 filed on Jun.7, 1995, now abandoned, which is a divisional of application Ser. No.08/161,715 filed Dec. 3, 1993, now U.S. Pat. No. 5,430,943 which is acontinuation-in-part of Ser. No. 07/990,792 filed Dec. 10, 1992 nowabandoned.

This invention relates to vegetation cutting devices, and moreparticularly to cutting attachments for use therewith.

Numerous cutting attachments have been provided for rotatably mountingto vegetation cutting and trimming devices. Most of these cuttingattachments, however, are not formed with skid plates which limitsnagging during use. In addition, many of these cutting attachments arenot self-cleaning and, as a result, collect debris during operation.Accumulated debris can limit the efficiency of the trimming device.Other cutting attachments are formed with skid plates and/or areconfigured so as to be self-cleaning, but have bodies formed from morethan one section (See U.S. Pat. No. 4,856,194). Each section of acutting attachment generally adds to the cost of manufacture andmultisectioned attachments require additional parts for assembly.Cutting attachments currently provided are also usually notinterchangeable between cutting devices made by various manufacturers.

Numerous cutting lines and strings and other accessories have also beenprovided for such cutting attachments. In general, these cuttingaccessories have a number of disadvantages. Many such cutting blades andstrings dull from use and become ineffective. Most such blades areeasily damaged if they encounter hard objects during use, particularlyif rigidly attached to the cutting attachment. These blades are alsogenerally ineffectual for cutting certain vegetation. Cutting stringscurrently available are also susceptible to fraying, which can reducethe cutting ability of the string. Cutting strings with protruding edgeshave also been found to cause significant wear to the cuttingattachment, often forming sharp edges therein which can undesirablysever the cutting string.

In general, it is an object of the present invention to provide acutting attachment which overcomes the limitations and disadvantages ofthe cutting attachments currently provided.

Another object of the invention is to provide a cutting attachment ofthe above character which has a unitary lightweight body.

Another object of the invention is to provide a cutting attachment ofthe above character which has a self-cleaning shape.

Another object of the invention is to provide a cutting attachment ofthe above character in which any cavities therein are formed fromgenerally smooth and outwardly inclined surfaces to inhibit weeds frombecoming caught in the same.

Another object of the invention is to provide a cutting attachment ofthe above character having a skid plate.

Another object of the invention is to provide a cutting attachment ofthe above character having an upper cavity and an accessory in the formof a cover plate which can be mounted on the body to overlie the uppercavity.

Another object of the invention is to provide a cutting attachment ofthe above character which can be readily coupled to various types ofcutting devices.

Another object of the invention is to provide a cutting attachment ofthe above character having improved cutting elements.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting elements include a cuttingblade having an inner cutting edge which can be exposed for use afterthe outermost leading cutting edge has worn.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting blades have serrated cuttingedges.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting blades are aerodynamic indesign.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting blades are yieldably mounted tothe cutting attachment for movement upon contact with an object.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting elements include a cuttingstring having an inner cutting edge which can be exposed after theoutermost cutting edge has worn.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting strings do not causesignificant wear to the cutting attachment during use thereof.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting strings inhibit frayingthereof.

Another object of the invention is to provide a cutting attachment ofthe above character in which the cutting strings have cutting edgeswhich are aerodynamically spiraled in longitudinal configuration.

Another object of the invention is to provide a cutting attachment ofthe above character which is provided with cutting elements in the formof cutting blades and cutting strings.

These and other objects are achieved in accordance with the invention byproviding a cutting attachment for use with a vegetation cutting devicehaving a rotatable drive member. The cutting attachment has a body witha generally planar coupling portion and a central axis of rotation.

In one embodiment, the body further includes a conical central wallportion extending outwardly and in a first direction from the couplingportion and with respect to the axis of rotation and a circular outerwall portion adjoining the central wall portion and extending generallyradially outwardly from the axis of rotation. The central wall portionhas a generally smooth inner surface which forms a conically-shapedfirst cavity disposed symmetrically about the axis of rotation. Thiscavity opens outwardly in the first direction so that it isself-cleaning during operation of the cutting device. The outer wallportion has a generally smooth outer surface free of projections andcavities which serves as a skid plate and is formed to inhibit snaggingon objects as the cutting attachment rotates. A second self-cleaningcavity which opens outwardly in an opposite second direction is formedby a generally smooth outer surface of the central wall portion and agenerally smooth inner surface of the outer wall portion which inclinesoutwardly and in the second direction with respect to the axis ofrotation.

Coupling means is carried by the coupling portion for coupling the bodyto the cutting device to cause rotation about the axis of rotation. Inone embodiment, the coupling means includes an adapter having first andsecond clamping elements for clamping the central portion of the cuttingattachment therebetween. The second clamping element include means forremovably securing the adapter to a rotatable drive member of a trimmingdevice.

A plurality of spaced apart radially extending cutting elements arecarried by the body for cutting vegetation as the body rotates about theaxis of rotation. These cutting elements can be in the form of cuttingblades and/or cutting strings. Cutting blades are provided withaerodynamic configurations, serrated edges, inner and outer cuttingedges (the inner edge being exposed after the outer edge is worn), andmeans for securing the blades to the cutting attachment which permitlongitudinal movement of the cutting blade with respect to the cuttingattachment. Cutting strings are provided with inner and outer cuttingportions (the inner cutting portion being exposed after the outercutting portion is worn), grooves for reducing fraying and spiraledconfigurations.

FIG. 1 is a top plan view of a cutting attachment of the presentinvention.

FIG. 2 is a cross-sectional view of the cutting attachment shown in FIG.1 taken along the line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view of the cutting attachment shown in FIG.1 taken along the line 3--3 of FIG. 1.

FIG. 4 is a fragmentary cross-sectional view, similar to FIG. 2, of thecutting attachment shown in FIG. 1 with another cover plate which can beused therewith.

FIG. 5 is a bottom plan view of another cover plate which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 6 is a cross-sectional view, similar to FIG. 2, of anotherembodiment of the cutting attachment of the present invention.

FIG. 7 is an enlarged view taken along the line 7--7 of FIG. 6.

FIG. 8 is a fragmentary side elevational view taken along the line 8--8of FIG. 6.

FIG. 9 is a cross-sectional view of an adapter which can be used withthe cutting attachment shown in FIG. 1 taken along the line 9--9 of FIG.10.

FIG. 10 is a fragmentary cross-sectional view taken along the line10--10 of FIG. 9.

FIG. 11 is a top plan view of a cutting blade for use with the cuttingattachment shown in FIG. 1.

FIG. 12 is a side elevational view taken along the line 12--12 of FIG.11.

FIG. 13 is a cross-sectional view taken along the line 13--13 of FIG.11.

FIG. 14 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 15 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 16 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 17 is a cross-sectional view taken along the line 17--17 of FIG.16.

FIG. 18 is a cross-sectional view, similar to FIG. 17, of anothercutting blade which can be used with the cutting attachment shown inFIG. 1.

FIG. 19 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 20 is a cross-sectional view taken along the line 20--20 of FIG.19.

FIG. 21 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 22 is a side elevational view of a cutting string which can be usedwith the cutting attachment shown in FIG. 1.

FIG. 23 is a cross-sectional view taken along the line 23--23 of FIG. 22with the opening of an eyelet superimposed thereon.

FIG. 24 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 25 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 26 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 27 is a side elevational view of another cutting string which canbe used with the cutting attachment shown in FIG. 1.

FIG. 28 is a cross-sectional view taken along the line 28--28 of FIG.27.

FIG. 29 is a side elevational view of another cutting string which canbe used with the cutting attachment shown in FIG. 1.

FIG. 30 is a fragmentary top plan view of another embodiment of thecutting attachment of the present invention.

FIG. 31 is a top plan view of another embodiment of the cuttingattachment of the present invention.

FIG. 32 is a cross-sectional view taken along the line 32--32 of FIG.31.

FIG. 33 is a top plan view of another embodiment of the cuttingattachment of the present invention.

FIG. 34 is a side elevational view taken along the line 34--34 of FIG.33.

FIG. 35 is a bottom view of the adapter shown in FIG. 9 taken along theline 35--35 of FIG. 9.

FIG. 36 is a fragmentary cross-sectional view of the cutting attachmentshown in FIG. 1 together with the adapter shown in FIG. 9.

FIG. 37 is a fragmentary cross-sectional view of another adapter whichcan be used with the cutting attachment shown in FIG. 1.

FIG. 38 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 39 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 40 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 41 is a cross-sectional view of another cutting string which can beused with the cutting attachment shown in FIG. 1 with the opening of aneyelet superimposed thereon.

FIG. 42 is a top plan view of another embodiment of the cuttingattachment of the present invention.

FIG. 43 is a top plan view of a cutting blade which can be used with thecutting attachment shown in FIG. 42.

FIG. 44 is a top plan view of another cutting blade which can be usedwith the cutting attachment shown in FIG. 42.

More in particular, as shown in FIG. 9 of the drawings, a conventionalvegetation trimming or cutting device 35 with which the cuttingattachment 36 of the present invention can be used is manufactured byInertia Dynamics Corp., 550 N. 54th Street, Chandler, Ark. 85226.Trimming device 35 has a member in the form of shield 37 with an innerclamping surface 38 which is generally planar. A rotatable drive memberin the form of drive shaft 39 perpendicularly extends through shield 37and protrudes from clamping surface 38. Drive shaft 39 is generallycircular in cross-section and has an axially aligned threaded bore 40which commences on the end thereof.

Cutting attachment 36 is comprised of a unitary one-piece rigid body 42which is generally conical in shape and formed from a suitable materialsuch as high strength plastic. Rigid body 42 has a central axis ofrotation 43 and includes a first or central wall portion 46 and a secondor outer wall portion 47 (See FIGS. 1 and 2).

Central wall portion 46 extends outwardly and in a first direction withrespect to axis 43, shown by first direction arrow 48 in FIG. 2, and hasa generally smooth inner surface 49, which forms a conically-shapedfirst or central cavity 51 disposed symmetrically about axis 43, and anopposite generally smooth outer surface 52. When cutting attachment 36is resting on a horizontal surface, axis 43 is generally vertical andfirst direction 48 points generally vertically upwardly. An inwardlyextending horizontal wall portion or lip 53 adjoins the upper and innerextremity of central wall portion 46 and is provided with a centrallydisposed hole or opening 58 therein which is generally circular incross-section. Coupling portion or lip 53 has an upper or outer surface61, which serves as the top surface of cutting attachment 36, and alower or inner surface 62, which serves as an inner surface for centralcavity 51.

Bottom or circular outer wall portion 47 adjoins central wall portion 46at the bottom or lower extremity thereof and extends generally radiallyoutwardly from axis 43. More particularly, outer wall portion 47 iscomprised of a first or generally horizontal part 71 which adjoinscentral wall portion 46 and extends radially outwardly from axis 43 anda second part 72 which adjoins first part 71 and extends generally in asecond direction, opposite first direction 48 and shown by seconddirection arrow 73 in FIG. 2, and radially outwardly from axis 43. Outerwall portion 47 has a generally smooth outer or bottom surface free ofprojections and cavities formed by generally planar lower surface 74 ofhorizontal part 71, which adjoins inner surface 49 of central wallportion 46, and generally arcuate outer surface 76 of a second part 72,which adjoins lower surface 74 and extends further radially outwardlyfrom axis 43 and in second direction 73. Outer wall portion 47 has agenerally smooth inner surface formed by upper generally planar surface77 of first part 71 and inner surface 78 of second part 72. Innersurface 78 is generally conical in shape, being inclined with respect toupper surface 77 and extending generally outwardly and in seconddirection 73 with respect to axis 43.

Inner surface 78 of outer wall portion 47, together with outer surface52 of central wall portion 46, form a second or outer cavity 81 incutting attachment 36. The opening to outer cavity 81 is bordered byinner and outer surfaces which are generally coplanar and horizontal.Outer surface 52 of central wall portion 46 is divided by an annularshoulder 86 which serves as the inner horizontal surface. Outer wallportion 47 ends in a generally annular end surface 87 which serves asthe outer horizontal surface. End surface 87 extends radially outwardlyfrom axis 43 and second part outer surface 76 to form one side of anannular ridge 88 formed on second part 72 of outer wall portion 47 andextending generally radially outwardly from surface 76.

A plurality of reinforcing bosses 90 are provided in outer cavity 81 andare approximately equivalently spaced circumferentially about outer wallportion 47, as for example 120° apart. Among other things, bosses 90contribute rigidity to body 42, being joined on one side to central wallportion 46 and on the other side to second part 72 of outer wall portion47. Each boss 90 has an upper surface 91 which is generally coplanarwith annular shoulder 86 and end surface 87. Bosses 90 can be hollowedin a manner known to those skilled in the art to reduce the weight ofcutting attachment 36 and be within the scope of the present invention.

An accessory in the form of a cover plate or ring 96 is included withincutting attachment 36 for those users wishing to cover outer cavity 81.Cover plate 96 is generally circular when viewed in plan, as illustratedin FIG. 1, and is formed from first or top and second or bottom planarsurfaces 97 and 98, as shown in FIG. 2. The cover plate is provided witha centrally disposed hole or opening 101 dimensioned to snuglycircumscribe and cooperatively mate with central wall portion 46. Whenmounted on body 42, bottom surface 98 of cover plate 96 abuts and isdisposed on annular shoulder 86 and end surface 87, with central wallportion 46 protruding through cover plate opening 101. For angularlypositioning cover plate 96 on body 42, bottom surface 98 thereof isprovided with a plurality of prongs or pins 102 extendingperpendicularly therefrom adjacent opening 101. Pins 102 areapproximately equivalently spaced from and circumferentially about axis43 and are dimensioned for disposition in an equal plurality ofvertically aligned bores 103 provided in annular shoulder 86 to receivepins 102.

Cutting attachment 36 includes a plurality of spaced-apart radiallyextending cutting elements carried by body 42 for cutting vegetation asthe body rotates about axis 43. The cutting elements can be in the formof cutting blades 121 mounted on outer wall portion 47 as shown inFIG. 1. Each blade 121 is formed from an elongate flat planar body 122of a high-impact plastic having first and second spaced-apart generallyparallel surfaces 123 and 126 and proximal or inner and distal or outerextremities 127 and 128 with an intermediate portion 129 therebetween(See FIGS. 11 through 13). First and second opposite and generallyparallel cutting edges 131 and 132 extend along intermediate portion 129and serve as sides to surfaces 123 and 126, with surfaces 123 and 126extending in directions generally perpendicular to edges 131 and 132.Each of edges 131 and 132 is vee-shaped in cross-section with anapproximately equivalent inclination angle, identified by inclinationangle 133 in FIG. 13 with respect to edge 131, and is formed by aninclined portion 123a on first surface 123 which slopes outwardly towardsecond surface 126. When body 122 is viewed in cross-section, as in FIG.13, inclined portions 123a extends generally linearly from one sidethereof to the other side thereof.

More specifically, elongate body 122 of cutting blade 121, when viewedin plan, has rounded proximal and distal extremities 127 and 128 andgenerally straight edges 131 and 132 which taper inwardly as they extendfrom proximal extremity 127 to distal extremity 128. First edge 131extends half-way around distal extremity 128 to meet second edge 132 atthe approximate centerline of cutting blade body 122, with inclinationangle 133 of first and second edges 131 and 132 gradually decreasing asthe edges extend around distal extremity 128 to so meet. In this manner,edges 131 and 132 become generally sharper and more pronounced as theyextend around distal extremity 128.

Inclination angle 133 of opposite edges 131 and 132 for portions ofintermediate body portion 129 of cutting blade 121 is also less thaninclination angle 133 for other portions of cutting blade 121, forexample, between such portions and each of proximal and distalextremities 127 and 128. This is a result of opposite inclined portions123a of intermediate body portion 129 extending arcuately inwardlytoward each other and the centerline of elongate body 122, asillustrated in FIG. 11 when cutting blade 121 is viewed in plan.

Securement means adapted to secure elongate body 122 to cuttingattachment 36 is carried by proximal extremity or mounting portion 127and is in the form of bore 136 which is generally circular incross-section and extends perpendicularly between surfaces 123 and 126through body 122.

Mounting means is provided for mounting cover plate 96 to rigid body 42and for pivotly mounting and attaching cutting blades 121 to outer wallportion 47 in a direction extending generally radially outwardly fromaxis of rotation 43. The mounting means includes a plurality of bolts141, each with a head 142, a shoulder 143 and a threaded portion 146.Bosses 90 are provided with bores 147 extending generallyperpendicularly through upper surface 91 thereof and first part lowersurface 74. Each bore 147 is centrally aligned about a pivot axis 148generally parallel to axis 43 and has a top bore portion 147a openingonto upper surface 91, a bottom bore portion 147b opening onto lowersurface 74 and a central bore portion 147c therebetween. Top and centralbore portions 147a and 147c are each generally circular incross-section, with central bore portion 147c having a smaller radialdimension than top bore portion 147a. Bottom bore portion 147b iscross-sectionally configured and sized to non-rotatably retain a nut151, and has a longitudinal dimension sufficient to recess nut 151therein. Cover plate 96 has a plurality bores 152 extending generallyperpendicularly through surfaces 97 and 98 spaced-circumferentiallyabout the cover plate. Bores 152 are generally circular in cross-sectionand have angular and radial dimensions with respect to axis 43 whichpermit them to align with rigid body bores 147. Bores 151 and 147 soalign when pins 102 on cover plate bottom surface 98 register withannular shoulder bores 103.

Cutting blade 121 is disposed over cover plate 96, generally abuttingtop surface 97 thereof, with bolts 141 extending through cutting bladebores 136 and cover plate bores 151. Each bolt shoulder 143 is adaptedto seat in top bore portion 147a and is concentric with central boreportion 147c. The distance between bolt head 142 and shoulder 143 isdimensioned to permit cutting blade 121 to pivot about axis 148 duringoperation of cutting attachment 36 on trimming device 35. Bolt head 142is provided with a transverse slot 153 on the top thereof which isadapted to receive a screwdriver so that bolt 141 can be threaded intoself-locking nut 151 seated within bottom bore portion 147b.

Additional cutting elements in the form of six cutting strings 161 arecarried by rigid body 42 and formed by three elongate flexible cuttinglines 162 made from a suitable material such as high-impact plastic.Cutting lines 162 are equivalently spaced circumferentially about rigidbody 42, for example 120° apart as shown in FIG. 1. Each cutting line162 is generally circular in cross-section with a central longitudinalaxis 163, and has at least three substantially continuous firstprojecting portions 166 extending longitudinally along the cutting lineand spaced-circumferentially about the outer radially extremity thereof(See FIGS. 22 and 23). Each cutting line 162 also has at least threesubstantially continuous second projecting portions 167 also extendinglongitudinally along the cutting line and spaced-circumferentially aboutthe outer radial extremity thereof. First projecting portions 166 areangularly spaced about axis 163 at equivalent intervals of approximately120° and second projecting portions 167 are angularly spaced about axis163 at equivalent intervals of approximately 120°, each secondprojecting portion 167 being located between adjoining first projectingportions 166.

Each first projecting portion 166 is formed by two generally angularlyspaced-apart side surfaces 168, which extend generally radiallyoutwardly from axis 163 to an approximate equivalent radial dimension171, and an interconnecting outer surface 172 formed by an arc of radialdimension 171 (See FIG. 23). Outer surface 172 serves as the outerradial extremity of each first projecting portion, with each firstprojecting portion 166 having a radial dimension 171 which isapproximately equivalent. Each side surface 168 is generally parallel tothe opposed side surface 168 of the adjoining first projecting portion166, and adjoins outer surface 172 to form a first or outer cutting edge173 which is approximately vee-shaped in cross-section. As such, eachfirst projecting portion 166 has two cutting edges 173. Opposed sidesurfaces 168 are angularly positioned about axis 163 in close proximityto each other so that three sets of adjacent cutting edges 173 areformed circumferentially about cutting string 161.

Second projecting portions 167 are recessed radially below outersurfaces 172 and between opposed side surfaces 168 of adjoining firstprojecting portions 166. Each second projecting portion 167 is formed bytwo surfaces 176 extending longitudinally along cutting line 162 andradially outwardly from the inner extremity of opposed side surfaces168. Surfaces 176 extend toward the opposed side surface 168 of theadjoining first projecting portion 166 to meet and form a second orinner cutting edge 177 which is generally vee-shaped in cross-section.Cutting edge 177 serves as the radial extremity of each secondprojecting portion 167, with each second projecting portion having anapproximately equivalent radial dimension 178 from axis 163 which isless than radial dimension 171 of first projecting portions 166.

Mounting means is provided by rigid body 42, in the form of flangedeyelets or grommets 186, for mounting cutting strings 161 on outer wallportion 47 in a direction extending generally radially outwardly fromaxis of rotation 43. Grommets 186 are generally tubular in shape and areprovided with an opening or bore 187 which extends longitudinallytherethrough (See FIG. 3). Bore 187 is formed by an inner surface 188which is generally circular in cross-section. Second part 72 of outerwall portion 47 is formed with adjoining pairs of grommets 186 extendingtherethrough. Adjoining grommets 186 are spaced circumferentially apartabout outer wall portion 47, with each grommet bore 187 generallyaligned with a radius extending outwardly from axis of rotation 43 (SeeFIG. 1). The central portion of cutting line 162 is disposed in outercavity 81 between two grommets 186. The spaced apart end portions of thecutting line 162 extend outwardly through the adjoining grommets 186.Outer surfaces 172 of first projecting portions 166 are adapted forengagement with inner surface 188 of grommets 186.

Coupling means is carried by central wall portion 46 and is adapted tocouple rigid body 42 to trimming device 35 to cause rotation of cuttingattachment 36 about axis of rotation 43. The coupling means comprises akeyway system 196 which includes a keyway formed by a pair of slots 197diametrically disposed on opposite sides of opening 58 in lip 53.Opening 58 and slots 197 are substantially similar to the relatedopening and slots described in U.S. Pat. No. 4,856,194 as part of thekeyway system described therein.

The coupling means further includes an adapter assembly 198 having firstor spacer and second or sleeve clamping elements 201 and 202,illustrated in FIGS. 9, 10, 35 and 36, made of a suitable material suchas high-strength plastic. Adapter assembly 198 also permits cuttingattachment 36 to be used with trimming devices manufactured by McCULLOCHCORP., Box 11990, Tucson, Ark. 85734-1990 and Homelite Textron, 14401Carowinds Blvd., Charlotte, N.C. 28241.

Disk-shaped spacer clamping element 201 is generally circular incross-section with first or upper and second or lower generally paralleland planar opposite surfaces 203 and 205. Upper and lower surfaces 203and 205 are provided with respective centrally disposed recesses 206 and207 therein. Lower surface 205 serves as a clamping surface, with recess207 having a diameter substantially equivalent to the diameter of lipopening 58. Spacer element 201 is provided with a centrally disposedbore 208 which extends perpendicularly through surfaces 203 and 205 andopens into the center of recesses 206 and 207 thereon. Bore 208 isadapted to snugly receive drive shaft 39 of trimming device 35 and is soconfigured and dimensioned. Spacer element 201 is a solid body, but canbe hollowed to reduce weight and manufacture costs and be within thescope of the present invention.

Sleeve clamping element 202 is generally cylindrical in shape and has afirst end portion or pilot 202a and an opposite second or lower endportion 202b, with an end 209, separated by a central portion or annularring 202c. End portions 202a and 202b are each generally circular incross-sectional configuration, with an approximately equal radialdimension. Annular ring 202c extends radially outwardly from endportions 202a and 202b, and has an annular clamping surface or shoulder210 which faces end portion 202a and extends perpendicularly outwardlytherefrom. Pilot 202a is provided with a pair of diametrically disposedears or keys 211 which extend upwardly from shoulder 210 and are adaptedto fit into the keyway provided by diametrically disposed slots 197 inopening 58. Keys 211 are part of keyway system 196. Lower end portion202b has an outer surface 212 with a plurality of splines 213 formedthereon which act as gripping means.

Sleeve element 202 is provided with a centrally disposed bore 215 whichextends longitudinally through end portions 202a and 202b and opens intoa recess or receptacle 216 provided in end 209. Bore 215 is adapted tosnugly receive drive shaft 39 and is so configured and dimensioned.Receptacle 216 is formed by a planar stop surface 217 which is generallyparallel with end 209 and an inner surface 218 which is generallyrectangular in cross-sectional configuration.

When cutting attachment 36 is mounted to trimming device 35, spacerelement 201 is first slipped over the protruding end of drive shaft 39.A disk-shaped washer 219 is sandwiched between trimming device clampingsurfaced 38 and spacer upper surface 203, with a portion of the washerseated in spacer recess 206. Cutting attachment 36 is next slipped overthe protruding end of drive shaft 39. Drive shaft 39 extends throughopening 58, and top surface 61 of lip 53 generally abuts lower surface205 of spacer element 201. Cutting attachment is positioned thereon sothat opening 58 is colinear about axis 43 with drive shaft 39. Sleeveelement 202 is disposed on the end of drive shaft 39 with the driveshaft extending into bore 215 thereof. Pilot 202a extends throughopening 58 and is disposed in spacer element recess 207 when keys 211angularly align about axis of rotation 43 with slots 191 in opening 58.Spacer element bore 208 and sleeve element bore 212 are aligned topermit the disposition of pilot 202a within spacer element recess 207.The interlocking spacer and sleeve elements 201 and 202 contribute tothe rigid connection of trimming device 35 and cutting attachment 36.

Means adapted to removably secure sleeve element 202 to drive shaft 59is provided in the form of a bolt 221, often part of trimming device 35,having an hexagonal head 222 and threaded portion 223. Bolt adaptermeans in the form of socket 225 is disposed and recessed in receptacle216 and can be included in this securement means. Socket 225, asillustrated in FIGS. 9 and 35, is generally U-shaped in cross-sectionand is provided with a recess 226 therein formed in part by an innersurface 227. Bolt head 222 is seated and recessed in socket recess 226,with inner surface 227 being cross-sectionally configured anddimensioned to non-rotatably receive hexagonal bolt head 222. Boltthreaded portion 223 extends into sleeve bore 215 and is threadedlydisposed in drive shaft bore 40.

Rotation of sleeve element 202 and/or cutting attachment 36 in atightening direction about axis 43 causes drive shaft 39 to approachstop surface 217 and socket 225 and the sleeve element to rotatably lockwith the drive shaft. Cooperatively mating socket 225 and sleeve innersurface 218 cause the socket to rotate with sleeve element 202, whilecooperatively mating bolt head 222 and socket inner surface 227 causebolt 221 to also rotate with the sleeve. No tools are needed formounting cutting attachment 36 to trimming device with adapter assembly198. Splines 213 provided on sleeve lower end portion 202b facilitatethe tightening of bolt 221 to drive shaft 39 and the resulting mountingof cutting attachment 36 to cutting device 35.

When cutting attachment 36 is so mounted to trimming device 35, spacerand sleeve elements 201 and 202 serve to clamp central wall portion 46of rigid body 42 between opposite facing clamping surface 205 andannular shoulder 210. Spacer and sleeve elements 201 and 202 and thebores therein are longitudinally dimensioned to permit this clamping.Keys 211 carried by sleeve element 202 and slots 197 provided in centralwall portion 46, which are included in keyway system 196 and act ascooperative key means, serve to ensure a positive rotational connectionbetween drive shaft 39 and cutting attachment 36. Cutting attachment 36includes self-locking means which causes the rotational force exerted oncutting attachment 36 by encountered objects to tighten bolt 221 withrespect to drive shaft 39. Bolt 221 and drive shaft bore 40 arecooperatively threaded to tighten when bolt 221 is exerted on by theserotational forces. The mating cross-sectional configurations of sleeveinner surface 218, socket inner surface 227 and bolt head 222 permittransference of these rotational forces from cutting attachment 36 andsleeve element 202 to bolt 221.

Operation and use of cutting attachment 36 shown in FIG. 1, with coverplate 96, cutting blade 121 and cutting strings 161 mounted thereon, isnow briefly described. Spacer and sleeve elements 201 and 202 are sizedand configured to permit economical and space efficient shipment thereofwith cutting attachment 36. Sleeve element 202 can be shipped in itsoperational position with pilot 202a disposed in central wall portionopening 58 as illustrated in FIG. 36. Spacer element 201 can be mountedon sleeve lower end portion 202b which is radially sized for relativelysnug disposition in spacer recess 207. Socket 225 is housed inreceptacle 216, retained in place by spacer element 201. Spacer recess207 is longitudinally sized so that both spacer and sleeve elements canbe housed within central cavity 51.

Cutting attachment 36 is secured to trimming device 35 by adapterassembly 198 in the manner discussed above. Various sockets 225 can beprovided with cutting attachment 36 for permitting mounting of thecutting attachment on a variety of trimming devices similar to trimmingdevice 35. Inner surfaces 227 of these sockets would vary inconfiguration and size to accommodate the respective mounting bolts ofthese trimming devices. Socket 225 can also be removed from sleeveelement 202 for larger mounting bolts, sleeve inner surface 218 beingsized and configured to non-rotatably receive the head of such a largerbolt.

Trimming device 35 is placed in operation in a conventional manner inclose proximity to the ground from which the weeds or grass are beingcut. Cutting attachment 36 is symmetrically balanced to permit highspeed rotation about axis 43. In this regard, opening 58, central cavity51 and outer cavity 81 are generally coaxial with axis 43. As soon ascutting attachment 36 rotates about axis of rotation 43, the centrifugalforces exerted on cutting blades and strings 121 and 161 cause them toextend generally radially outwardly from axis 43 for encounteringvegetation.

One of edges 131 or 132 of cutting blade 121 is forwardly projectingduring rotation of cutting attachment 36 and serves as a leading cuttingedge for encountering and cutting the desired vegetation. The other edgeon cutting blade 121, opposite the leading edge, serves as a trailingedge. The relatively small inclination angles 133 at intermediateportion 129 and distal extremity 128 of cutting blade elongate body 122,which are each smaller than inclination angle 133 at the other portionsof the leading and trailing cutting edges 131 and 132 of elongate body122 and the inclination angle of other conventional cutting blades,serves to reduce the frictional drag experienced by cutting blade 121 asit slices through the air. In this manner, the aerodynamically efficientconfiguration of cutting blade 121 serves to increase the speed at whichthe cutting blade rotates about cutting attachment 36 and therebyincrease the cutting forces exerted on encountered vegetation by thecutting blade. It also reduces the drag on the cutting and drivesystems.

The cross-sectional configuration of cutting string 161 serves severalfunctions. It has been found, for example, that cutting strings havingoutwardly projecting cutting edges as radial extremities which bear oninner bore-forming surfaces (such as surfaces 188 of grommets 186)during use of cutting attachment 36 tend to cause significant wear tothese grommet inner surfaces. Arcuate outer surfaces 172 of firstprojecting portions 166 generally conform with the circularcross-sectional configuration of bores 187 in grommets 186 and,accordingly, reduce the wear on inner bore-forming surfaces 188. It hasalso been found that cutting strings with generally smooth arcuate outersurfaces such as surface 172 are more aerodynamic than cutting stringswith projecting edges which serve as the radial extremity thereof.Cutting string 161 is formed with minimal air pockets which can causevariations in cutting height.

Cutting string 161 has two sets of cutting edges, one set which isavailable at the initial use and the second set which becomes availableafter the first set is worn away, and as a result can be said to haverenewable edges. Outer cutting edges 173, which are aligned in pairscircumferentially about cutting string 161, serve as initial cuttingedges during operation of the cutting strings. As outer protectingportions 166 are worn away during operation of trimming device 35,through dulling and/or fraying, cutting edges 177 of inner protectingportions 167 are exposed so as to extend the cutting life of the cuttingstring. Since cutting string wear occurs near the tip of the string, thegrommet protecting characteristics of first projecting portions 166 arenot affected by this wear.

The cross-sectional configuration of cutting string 161 also serves tocontribute significant mass to the cutting string, as illustrated inFIG. 23 where the opening of an eyelet is superimposed thereon. Greatermass tends to increase cutting power. Many conventional cutting stringsare formed with a plurality of cutting edges having voids therebetweenwhich decrease the mass of the cutting string.

Each of cutting blades 121 and cutting strings 161 can move from a firstposition extending generally radially outwardly from cutting blade body42 for cutting vegetation to a second generally out-of-the-way positionwherein the blades and strings are within the outer confines of body 42.With respect to cutting blades 121, the mounting means discussed abovewhich permits the cutting blades to pivot in a plane generallyperpendicular to axis of rotation 43 and the generally planar alignmentof annular shoulder 86 and end surface 87 which the cutting blades andgenerally planar cover plate 96 overlie, permit cutting blades 161 topivot to a second position generally overlying cover plate 96 when thecutting blades encounter an obstacle.

With respect to cutting strings 161, annular ridge 88, formed on theouter radial extremity of outer wall portion 47 and generally adjacentto the opening of grommet bores 187 and the cutting strings extendingoutwardly therefrom, serves as a protection ring for protecting thecutting strings from objects encountered by them and cutting attachment36 during operation of trimming device 35. Most desirably, ridge 88should project outwardly from outer surface 76 a distance at least equalto the thickness of cutting lines 162. It should be appreciated thatridge 88 can have other configurations and locations on body 42,including a location below grommets 186, and be within the scope of thepresent invention. Cutting lines 162 are locked in cavity 81 where theyare protected from encountering objects and thus less susceptible towear.

It should also be appreciated that a cutting attachment 36 having afewer or greater number of cutting blades 121 and/or cutting strings 161mounted thereon is within the scope of the present invention. Forexample, cutting attachment 36 could have two diametrically opposedcutting blades 121 mounted thereon and/or two diametrically opposedcutting lines 162 mounted thereon. Most desirably, cutting blades 121and cutting strings 161 carried by body 42 should be symmetricallymounted thereon so as to maintain the balance of cutting attachment 36during its rotatable use on trimming device 35. In addition, cuttingstrings 161 can be mounted to cover plate 96 and be within the scope ofthe present invention.

Relatively smooth bottom and outer surfaces 74 and 76 of outer wallportion 47 serve as a skid plate for cutting attachment 36 and areformed generally free of projections and cavities to inhibit snagging onobjects as cutting attachment 36 rotates during operation. Bottom boreportions 147b which house nuts 151 therein are disposed on the bottomand outer surfaces of the outer wall portion so as to be free of anygenerally protruding rims or edges capable of catching on objects.Self-locking nuts 151 are recessed within bores 147 so as to beprotected from damage and maintain the effectiveness of the skid plate.

Rigid body 42 is also constructed so that central wall portion 46 has agenerally smooth inner surface 49 which is conical in shape forinhibiting the collection of weeds, grass and debris within centralcavity 51. Inner surface 49, which opens outwardly in first direction48, is generally self-cleaning during operation of trimming device 35and causes any such weeds, grass or debris therein to be thrownoutwardly away from axis of rotation 43 and downwardly from cuttingattachment 36.

Among its various functions, cover plate 96 serves to further hinder thecollection of debris within outer cavity 81. The cover plate also addsadditional rigidity to cutting attachment 36. In addition, unlikecutting attachments formed from two pieces bolted together, such as thatdisclosed in U.S. Pat. No. 4,856,194, failure of cover plate fasteningbolts 141 will not result in pieces of the cutting attachment flyingloose. Because cover plate 96 is carried circumferentially about centralwall portion 46, a loose cover plate will remain attached to cuttingattachment 36.

Cutting attachment 36 can be operated without cover plate 96 mountedover outer cavity 81 and be within the scope of the present invention.Should cutting attachment 36 be so operated, outer cavity 81, whichopens outwardly in second direction 73, is also generally self-cleaningduring operation of cutting attachment. Outer wall portion inner surface78 extends radially outwardly and, in the same manner as central wallportion inner surface 49, inhibits the collection of weeds, grass anddebris therein.

The unitary and relatively simple design of cutting attachment 36results in lower manufacturing costs than cutting attachments withcomparable features which are generally comprised in two or moresections. Rigid body 42 is also relatively lightweight in comparison tocomparable cutting attachments and can be adapted with cover plate 96for covering outer cavity 81 should the user of cutting attachment 36 sodesire.

The cover plate for use on rigid body 42 can have other configurationsand be within the scope of the present invention. For example, inanother embodiment illustrated in FIG. 4, a generally planar cover platesubstantially similar to cover plate 96 is provided. Cover plate 231 hasparallel planar and opposite first or top and second or bottom surfaces232 and 233 and is provided with a centrally disposed opening or hole236 therethrough. Opening 236 is dimensioned and configured to snuglyabut outer surface 52 of central wall portion 46. Bottom surface 233 isformed with an annular reinforcing ring 237 adjacent opening 236 whichextends downwardly therefrom in first direction 48 and ends with anannual and planar support surface 238 generally parallel with surfaces232 and 233. Support surface 238 is formed with prongs or pins 241spaced radially and circumferentially thereabout and aligned tocooperatively mate with bores 103 in annular shoulder 86 of rigid body42.

Cover plate 231 is designed to be mounted on outer wall portion 47 sothat cutting blades 121 are sandwiched between cover plate bottomsurface 233 and outer wall portion end surface 87. In this regard,support ring 237 extends from bottom surface 233 a distancesubstantially equivalent to the width of cutting blade elongate body122. The cover plate is provided with three bores 242 perpendicularlyextending through surfaces 232 and 233 and spaced radially andcircumferentially thereabout to align with bores 147 in outer wallportion 47. Means for mounting and attaching cover plate 231 and cuttingblades 121 to outer wall portion 47 is substantially similar to themounting and attaching means described above with respect to cover plate96, and includes bolts 243 substantially similar to bolts 141. Bolts 243have heads 246 which seat and are recessed in countersinks 247 providedin cover plate 231.

In operation and use, cover plate 231 serves substantially the samepurpose as cover plate 96, except that cover plate 231 permits cuttingblades 121 to pivot to a recessed position substantially within theinterior of cutting attachment 36. Cutting blades 121 can pivot aboutbolts 246 from a first or a cutting position extending radiallyoutwardly from outer wall portion 47 to a second or recessed positiongenerally overlying outer cavity 81 and underlying cover plate 231.

In another embodiment, a generally planar cover plate 256 is providedwhich includes an inner ring 257 having a centrally disposed opening 258configured and dimensioned to snugly circumscribe central wall portion46 (See FIG. 5). Ring 257 has a bottom surface 261 which abuts annularshoulder 86 and is provided with three prongs or pins 262 extendingoutwardly therefrom in first direction 48 and spaced radially andcircumferentially about the ring so as to cooperatively mate withannular shoulder bores 103. Ring 257 further includes three planar armsegments 263 extending radially therefrom and spaced circumferentiallythereabout so as to overly bosses 90. Each arm segment 263 has a distalor outer end portion 263a disposed on outer wall portion end surface 87and is provided with a bore 266 extending therethrough and aligned withbores 147 in bosses 90. Cover plate 256 is mounted on body 42 insubstantially the same manner as cover plate 231, with cutting blades121 sandwiched between cover plate 256 and surfaces 91 and 87 of outerwall portion 47, and serves as a reinforcing ring when mounting cuttingblades 121 to body 42. Means for mounting and attaching cover plate 256and cutting blades 121 includes bolts 243. Cover plate 256 is providedwith countersinks 267 for seating bolt heads 246.

The cutting attachment can have other configurations and be within thescope of the present invention. For example, a cutting attachment 276formed from a unitary rigid body 277 having an axis of rotation 278 isshown in FIGS. 6 through 8. Body 277 includes a central wall portion 281centered on axis 278 and extending radially outwardly from axis 278 andin a first direction (shown by first direction arrow 282 in FIG. 6) atan angle from axis 278 greater than the inclined angle from axis 43 ofcentral wall portion 46. Central wall portion 281 has inner and outersurfaces 283 and 286, inner surface 283 forming a self-cleaning first orcentral cavity 287 which is symmetrically disposed about axis 278 and isconical in shape. An inwardly extending horizontal wall portion or lip288 generally perpendicular to axis 278 adjoins the inner or upperextremity of central wall portion 281 and has an inner surface 291 whichserves as an end surface to central cavity 287 and an opposite uppersurface 292. Coupling portion or lip 288 is provided with a centrallydisposed opening 293 therein provided with diametrically opposed slots296 substantially similar to slots 197 in rigid body 42.

A bottom or outer wall portion 297 adjoins the outer or lower extremityof central wall portion 281 and extends generally radially outwardlyfrom axis 278. Outer wall portion 297 is formed from a first part 298which extends radially outwardly and slightly in a second direction(opposite to first direction 282 and shown by second direction arrow 301in FIG. 6) so as to be slightly conical in shape, a second part 302extending radially outwardly and in second direction 301 at a lesserangle from axis 278 than the corresponding angle of first part 298 so asto be also conical in shape, and a short third part 303 extending insecond direction 301 so as to be tubular in shape. First, second andthird parts 298, 302 and 303 have respective opposite and generallysmooth inner and outer surfaces 306 and 307, 308 and 311, and 312 and313. Inner surfaces 306, 308 and 312, together with central wall portionouter surface 286, form a self-cleaning second or outer cavity 316.Outer surfaces 307 and 311 serve as a skid plate. Third part 303 isprovided with a planar annular end surface 317 which is generallyperpendicular to axis 278 and forms part of an annular protection ridge318 projecting radially outwardly from third part outer surface 313.

Cutting elements such as cutting blades 121 can be mounted on cuttingattachment body 277 and, in this regard, outer wall portion 297 isprovided with a plurality of bosses 321 formed in outer cavity 316 whichare substantially similar to bosses 90 and are approximatelyequivalently spaced circumferentially around the outer wall portion.Each boss is provided with a bore 322 through the boss and outer wallportion 297 which is substantially similar to bore 147, having a topbore portion 322a, a bottom bore portion 322b and a central bore portion322c therebetween. Means for pivotally mounting and attaching cuttingblades 121 to outer wall portion 297 is substantially similar to themeans for mounting and attaching cutting blades 121 to cuttingattachment body 42 and includes bolts 323, each with a head 326, ashoulder 327 and a threaded portion 328, and a nut 331. When a cuttingblade 121 is mounted to rigid body 277, as illustrated in FIG. 6, thecutting blade rides on the top of boss 321 and annular end surface 317and self-locking nut 331 is recessed within bottom bore portion 322b soas not to contact objects encountered by cutting attachment 276.

A plurality of cutting elements such as cutting strings 161 formed fromcutting lines 162 can also be carried by cutting attachment 276 and bespaced circumferentially about rigid body 277 in substantially the samemanner as the cutting strings are spaced about cutting attachment body42. Means for mounting and attaching cutting lines 162 to outer wallportion 297 includes an opening 336 extending through surfaces 308 and311 of second part 302 (See FIGS. 6 through 8). A cross member 337substantially adjacent inner surface 308 and coplanar with axis 278transverses opening 336 and assists in securing cutting line 162 torigid body 277. The central portion of cutting line 162 is looped aboutcross member 337. The end portions of cutting line 162 extend from crossmember 337 in opposite angular directions about outer cavity 316 andthrough flanged tubular grommets 338, substantially similar to grommets186, formed in outer wall portion third part 303. Outer wall portionsecond part 302 and cross member 337 formed in opening 336 thereof aredimensioned so that cutting line 162 is recessed within opening 336 soas not to engage objects encountered by cutting attachment 276.

Cutting attachment 276 includes coupling means carried by central wallportion 281 adapted to couple rigid body 277 to a cutting device such astrimming device 35 and cause rotation about axis 278. The coupling meansis in the form of a keyway system substantially identical to keywaysystem 196 and including lip opening 293 with slots 296 formed therein.Adapter assembly 198 is used in rotatably coupling cutting attachment276 to trimming device 35.

In operation and use, cutting attachment 276 operates in substantiallythe same manner as cutting attachment 36 with the configuration andsmooth surfaces of central and outer wall portions 281 and 297 formingcavities which inhibit the collection of grass, weeds and debris bycausing them to be flung out from the cutting attachment. The generallysmooth skid plate surfaces of outer wall portion 297 are generally freeof projections and cavities capable of snagging objects encountered bycutting attachment 276. As a result, outer wall portion 297 enablescutting attachment 276 to skid over objects encountered by it. Cuttingblades and strings 121 and 161 are each movable from an operableposition extending radially outwardly from axis 278 to a nonoperableout-of-the-way position within the confines of rigid body 277 so as tominimize damage thereto when the rotating cutting attachment engagesharmful objects.

Cutting attachments 36 and 276 can be used with other conventionalvegetation cutting or trimming devices besides trimming device 35. Asstated above, keyway system 196 described above is substantially similarto the cutting attachment keyway system described in U.S. Pat. No.4,856,194, the terms and provisions of which are incorporated herein bythis reference. In the same manner as the cutting attachments describedin U.S. Pat. No. 4,856,194, cutting attachments 36 and 276 can be usedwith a conventional trimming device such as manufactured by EchoIncorporated of Lake Zurich, Ill., 60047 which is described in somedetail in U.S. Pat. No. 4,856,194.

Cutting elements in the form of cutting blades for use on cuttingattachments can have other configurations and be within the scope of thepresent invention. For example, a cutting blade 376 is illustrated inFIG. 14 which is formed from an elongate flat planar body 377 having aproximal extremity or mounting portion 378 and a cutting portion 381formed from a generally straight first part 382 and a generally straightsecond part 383 at an oblique angle to first part 382 and having adistal extremity 384. Mounting portion 378 includes a bore 376 extendingtherethrough which serves as means for securing and pivotally mountingcutting blade 376 to a cutting attachment. Cutting portion 381 is formedwith first and second opposite serrated cutting edges 387 and 388 whichare each generally vee-shaped in cross-section and formed from aplurality of teeth 391. Elongate body 377 has first and secondspaced-apart generally parallel surfaces 392 extending between edges 387and 388 in directions generally perpendicular to the edges. Each ofsurfaces 392 have inclined portions 392a along the side thereof whichserve to form edges 387 and 388.

In operation and use, cutting blade 376 is mounted to a cuttingattachment such as cutting attachment 36 in the manner discussed abovewith one of serrated edges 387 and 388 positioned as a leading edge andthe other as a trailing edge. Teeth 391 thereon assist in the trimmingof vegetation encountered by rotating cutting attachment 36, acting toboth saw and cut the vegetation as cutting blade 376 slicestherethrough. Cutting blade 376 can be mounted on the cutting attachmentwith second part 383 angled toward the rotational direction of travel oraway therefrom, depending upon the needs of the user. In most instances,it has been found that second part 383 should be angled toward thedirection of travel when larger vegetation is desired to be cut. When soconfigured, the shearing forces of cutting blade 376 tend to be higherthan when the cutting blade is positioned with second part 383 angledaway from the direction of travel. On the other hand, positioning ofsecond part 383 so that it angles away from the direction of travelfacilitates better positioning of cutting blade 376 within the confinesof the cutting attachment body 377 in the event an object is struck bythe blade.

In another embodiment, a cutting blade 396 similar to cutting blade 376is provided which is formed from an elongate flat planar body 397 havinga mounting portion or proximal extremity 398, substantially similar tomounting portion 378, and a cutting portion 401 (See FIG. 15). Cuttingportion 401 has a distal extremity 402, first and second oppositecutting edges 403 and 406 which are each generally vee-shaped incross-section and first and second spaced-apart generally parallelsurfaces 407 which extend between the edges and have inclined portions407a which form the edges. First cutting edge 403 is serrated, beingformed from a plurality of teeth 498. Cutting portion 401 is generallyarcuate or curved when viewed in plan and has operational featuressimilar to cutting blades 161 and 376 described above.

In another embodiment, a cutting element in a form of cutting blade 411is provided as illustrated in FIGS. 16 and 17. Cutting blade 411 isformed from an elongate flat body 412 having a mounting portion 413 anda cutting portion 416 which includes a distal extremity 417. Mountingportion 413 is provided with a bore 418 therethrough which is generallyoblong in cross-sectional shape, with the longer cross-sectionaldimension generally aligned with longitudinally extending body 412.Cutting portion 416 is formed with first and second opposite cuttingedges 421 and 422 which extend along the side thereof and, like edges131 and 132 of cutting blade 121, are generally vee-shaped incross-section. First and second spaced-apart generally parallel surfaces423 and 426 extend between edges 421 and 422 in directions generallyperpendicular to the edges.

Each of surfaces 423 and 426 are provided with a plurality of parallelvee-shaped grooves or indentations 427 situated between first and secondcutting edges 421 and 422 which generally extend the length of surfaces423 and 426 in directions parallel to the cutting edges. Cutting portion416 is further provided with a plurality of spaced-apart parallelreinforcing portions or ribs 428 which extend generally transversely ofcutting edges 421 and 422. More particularly, reinforcing ribs 428extend perpendicularly between the cutting edges and across indentations427 and serve to segment the aligned indentations 427. As illustrated inFIG. 17, indentations 427 serve to partition cutting portion 416 into aplurality of parallel knife elements 431 which are in juxtaposition witheach other and have opposed and interconnected inner cutting edges 432.Each knife element 431 has a cross-section which is generally in theshape of a parallelogram or diamond with the related inner cutting edges432 thereof being evidenced by two of the opposite corners of theparallelogram or diamond. Reinforcing ribs 428 further interconnectknife elements 431.

In operation and use, oblong bore 418 serves as means for securing andpivotally mounting cutting blade 411 to a cutting attachment such ascutting attachment 36 or 276 and also serves as means to permit cuttingblade 411 to move longitudinally with respect to the cutting attachmentin the event the cutting blade strikes an object during operation oftrimming device 35. Such longitudinal movement can reduce damage tocutting blade 411 in these instances by permitting it to move out ofharms way. Once contact with the encountered object has ceased, thecentrifugal force exerted on cutting blade 411 during operation of thecutting attachment causes the cutting blade to extend radially outwardlyagain to its outer-most cutting position. Bore 418 also serves todecrease the amount of friction generated heat in mounting portion 413by expanding the exposed cooling surface area in the bore.

Inner cutting edges 432 created by indentations 427 can be exposed afterthe outer-most leading cutting edge 421 or 422 of cutting blade 411 hasworn out or is no longer cutting effectively. In this regard, theleading knife element 431, which includes the leading cutting edge 421or 422, can be removed either through wear or through manual separationby slicing or cutting through the related leading outer-most alignedindentations 427 on opposite surfaces 423 and 426. Cutting blade 411 canbe used so that either first cutting edge 421 or second cutting edge 422acts as a leading cutting edge. Changing a cutting edge 421 or 422 froma leading to a trailing cutting edge, or vice versa, is accomplished byturning cutting blade 411 upside down or, where possible, reversing therotation direction of trimming device 35.

Cutting blade 411, with inner cutting edges 432, can be said to haverenewable edges. One of the advantages of cutting blade 411 is increasedcutting performance and efficiency. The renewable feature provides forcontinually sharp edges and increases the cutting life of cutting blade411. Maintenance in the form of resharpening of the cutting edges ofcutting blade 411 is reduced if not eliminated. When compared toexisting cutting systems, the use of renewable edge cutting blades suchas cutting blade 411 on small electric cordless rotary devices cangreatly improve the overall cutting power of these devices. In thismanner, the cutting power of these small electric cutting devices can beincreased to the level of larger cutting device models, such as smallpetroleum powered devices. These increases in cutting power andefficiency result in a shortened work time for a given project, reducedpollution and use of natural resources and savings of money.

In another related embodiment shown in cross-section in FIG. 18, acutting blade 436 is provided which, when viewed in plan, issubstantially identical to cutting blade 411. Cutting blade 436 isformed with first and second cutting edges 437 and 438 and first andsecond spaced-apart generally parallel surfaces 441 and 442.Indentations 443 and reinforcing portions or ribs 446 are provided onfirst surface 441, but not second surface 442, and serve to create aplurality of knife elements 447 which are each generally triangular inshape when viewed in cross-section. Cutting blade 436 operates insubstantially the same manner as cutting blade 411.

In another embodiment of a cutting element similar to cutting blades 411and 436, a cutting blade 451 formed from an elongate flat planar body452 having a distal extremity or mounting portion 453 and an adjacentcutting portion 456 is provided (See FIGS. 19 and 20). Mounting portion453 is provided with a bore 457 which is circular in cross-section andserves as means for pivotally securing and mounting cutting blade 451 toa cutting attachment such as cutting attachment 36 or 276 for use ontrimming device 35. Cutting portion 456 has a distal extremity 458 andis formed with first and second opposite cutting edges 461 and 462 whichextend along the sides thereof between mounting portion 453 and distalextremity 458, edges 461 and 462 each being generally vee-shaped incross-section. First and second spaced-apart generally parallel surfaces463 and 466 extend between edges 461 and 462 in directions generallyperpendicular to the edges, with first surface 463 having inclinedportions 463a along each side thereof to form the cutting edges. Firstsurface 463 is also provided with a plurality of parallel U-shapedindentations 467 extending diagonally of first and second cutting edges461 and 462. As illustrated in FIG. 20, indentations 467 form aplurality of parallel knife elements 468 with interconnected innercutting edges 471 shown as interconnected corners of adjacent triangles.

In operation and use, cutting blade 451 is used in a manner similar tocutting blade 436. It has been found that cutting blades sometimes wearto form a diagonal edge between the leading cutting edge and the distalextremity of the cutting blade. This diagonal edge is at an oblique orinclined angle with respect to the leading cutting edge. Cutting blade451 can be used in situations which result in this type of wear, withinner cutting edges 471 which generally face the direction of travel ofcutting blade 436 serving as additional cutting edges after the leadingcutting edge of the leading knife element 468 is worn. Theinterconnection between opposed inner edges 471 of adjacent knifeelements 468 is sufficient to support the knife elements during use ofcutting blade 451 without need of reinforcing ribs similar toreinforcing ribs 446. Cutting blade 451 could have indentations onsecond surface 466 so as to form knife elements similar to those shownin FIG. 17 and be within the scope of the present invention.

Another cutting element suitable for use with cutting attachments 36 or276 is illustrated in FIG. 21. Cutting blade 476 is formed from anelongate flat planar body 477 having a proximal extremity or mountingportion 478 and a cutting portion 481 which includes a first or centralpart 482 adjacent mounting portion 478 and a second part 483 adjoiningcentral part 482. Second part 483 includes distal extremity 486 forcutting blade 476. Mounting portion 478 is provided with a bore 487therethrough which serves as means for securing and pivotally mountingcutting blade 476 to cutting attachments 36 or 276 for use on a trimmingdevice 35. Cutting portion 481 is formed with first and second oppositecutting edges 488 and 491 which extend along the sides thereof betweenmounting portion 478 and distal extremity 486 and are each generallyvee-shaped in cross-section. Cutting portion 481 is further providedwith first and second spaced-apart generally parallel surfaces 492extending between cutting edges 488 and 491 in directions generallyperpendicular to the cutting edges.

Second part 483 adjoins first part 482 at an oblique angle and isprovided with a plurality of parallel generally vee-shaped indentations496 situated between first and second cutting edges 488 and 491 andextending along the length of first part 482 in directions parallel tothe cutting edges on first surface 492. Spaced-apart parallelreinforcing portions or ribs 497 extend generally transversely acrosssecond part 483 and are generally perpendicular to cutting edges 488 and491.

Cutting blade 476 has aspects similar to cutting blades 376 and 411 andis mounted to a cutting attachment on a trimming device 35 for use andoperation substantially similar to those cutting blades.

Cutting elements in the form of cutting strings for use on cuttingattachments can have other configurations and be within the scope of thepresent invention. For example, a cutting string 506 formed from anelongate flexible cutting line 507 is illustrated in cross-section inFIG. 24. Cutting line 507 is made from a suitable material such ashigh-impact plastic and has a central longitudinal axis 508 shown in endview in FIG. 24. Cutting line 507 is generally rectangular incross-sectional shape and has at least four substantially continuousfirst projecting portions 511 extending longitudinally along the cuttingline and spaced-circumferentially about the outer radially extremitythereof. Cutting line 507 also has at least four substantiallycontinuous second projecting portions 512 also extending longitudinallyalong the cutting line and spaced-circumferentially about the outerradial extremity thereof.

First projecting portions 511 are angularly spaced about axis 508 atequivalent intervals of approximately 90° and second projecting portions512 are angularly spaced about axis 508 at equivalent intervals ofapproximately 90°, each second projecting portion 512 being locatedbetween adjoining first projecting portions 511. Pairs of firstprojecting portions 511 are diametrically opposed with each other, andpairs of second projecting portions 512 are also diametrically opposedto each other.

Each first projecting portion 511 is formed by two spaced-apart parallelside surfaces 513, which extend generally outwardly from axis 508 to anapproximate equivalent radial dimension 516, and an interconnectingouter surface 517 formed by an arc of radial dimension 516. Outersurface 517 serves as the outer radial extremity of each firstprojecting portion, with each first projecting portion 511 having aradial dimension 516 which is approximately equivalent. Each sidesurface 513 adjoins outer surface 517 to form a first or outer cuttingedge 518 which is an approximate right angle in cross-section. As such,each first projecting portion 511 has two opposite cutting edges 518.

Second projecting portions 512 are recessed radially below outer surface517 between side surfaces 513 of adjoining first projecting portions511. Each second projecting portion 512 is formed by two surfaces 521extending longitudinally along cutting line 507 and radially outwardlyfrom the inner extremity of the side surfaces 513 of said adjoiningfirst projecting portions 511. Surfaces 521 extend outwardly and towardeach other and meet to form a second or inner cutting edge 522 which isgenerally vee-shaped in cross-section. Cutting edge 522 serves as theradial extremity of each second projecting portion 512, with each secondprojecting portion having an approximately equivalent radial dimension523 from axis 508 which is less than radial dimension 516 of firstprojecting portions 511.

Cutting line 507 mounts to cutting attachments 36 and 276 insubstantially the same manner as cutting line 162. Cutting string 506operates in substantially the same manner as cutting string 161. Amongother things, first projecting portion outer surface 517 serves toreduce the wear on the inner bore-forming surfaces of grommets 186 and338. First projecting portion cutting edges 518 act as initial cuttingedges, and second projecting portion cutting edges 522 act as secondaryor inner cutting edges which are generally exposed after first cuttingedges 518 are worn. Cutting line 507 has considerable mass for enhancingits cutting force.

In another embodiment, a cutting string 531 similar to cutting strings161 and 506 is shown in FIG. 25. Cutting string 531 is formed from anelongate flexible cutting line 532 made from a suitable material such ashigh-impact plastic and having a central longitudinal axis 533 shown inend view in FIG. 25. Cutting line 532 is generally rectangular incross-sectional shape and has at least four substantially continuousfirst and second projecting portions 536 and 537 extendinglongitudinally along the cutting line which are eachspaced-circumferentially about the outer radially extremity thereof.Each set of projecting portions 536 and 537 are angularly spaced aboutaxis 533 at equivalent respective intervals of approximately 90°, eachsecond projecting portion 537 being located between adjoining firstprojecting portions 536. Pairs of first projecting portions 536 andpairs of second projecting portions 537 are each diametrically opposedto each other.

Each first projecting portion 536 is formed by two opposite sidesurfaces 538 which extend generally outwardly from axis 533 and towardeach other to meet and form a first or outer cutting edge 541 which isgenerally vee-shaped in cross-section. First cutting edges 541 each havean approximate equivalent radial dimension 542 and serve as the outerradial extremity of first projecting portions 536.

Second projecting portions 537 are recessed radially below cutting edges541 of first projecting portions 537, and are each formed by two sidesurfaces 543 which extend radially outwardly from the inner extremity ofside surfaces 538 of adjoining first projecting portions 536 and towardeach other to meet and form a second or inner cutting edge 546 which isgenerally vee-shaped in cross-section. Second cutting edges 546 eachhave an approximate equivalent radial dimension 547 from axis 533 whichis less than radial dimension 542 of first projecting portions 536, andserve as the outer radial extremity of second projecting portions 537.

Cutting line 532 mounts to cutting attachments 36 and 276 insubstantially the same manner as cutting line 162. cutting string 531operates in a manner similar to cutting string 161, with firstprojecting portion cutting edges 541 acting as initial cutting edges andsecond projecting portion cutting edges 546 acting as secondary or innercutting edges which are generally exposed after first cutting edges 541are worn.

In another embodiment, a cutting string 551 similar to cutting string531 and formed from an elongate flexible cutting line 552 made from asuitable material such as high-impact plastic is provided (See FIG. 26).Cutting line 552 has a central longitudinal axis 553, shown in end viewin FIG. 26, and is generally rectangular in cross-sectional shape.Cutting line 552 has at least four substantially continuous first andsecond projecting portions 556 and 557 extending longitudinally alongthe cutting line which are each spaced-circumferentially about the outerradially extremity thereof. Each set of projecting portions 556 and 557are angularly spaced about axis 553 at equivalent respective intervalsof approximately 90°, each second projecting portion 557 being locatedbetween adjoining first projecting portions 556. Pairs of firstprojecting portions 556 and pairs of second projecting portions 557 areeach diametrically opposed to each other.

Each first projecting portion 556 is generally rectangular-shaped incross-section and is formed by two generally perpendicular first sidesurfaces 558 which extend generally outwardly from axis 553 and awayfrom each other and two second side surfaces 561, each perpendicularlyadjoining the related first side surface 558, which extend generallyoutwardly from axis 553 and toward each other. Second side surfaces 561meet at an approximate right angle to form a first or outer cutting edge562. First cutting edges 562 each have an approximate equivalent radialdimension 563 and serve as the outer radial extremity of firstprojecting portions 556. Each first side surface 558 is generallyparallel to the opposed first side surface 558 of the adjoining firstprojecting portion 556, and joins its related second side surface 561 toform a second cutting edge 566. Second side surfaces 561 of adjoiningfirst projecting portions are generally coplanar and form a side ofcutting line 552.

Second projecting portions 557 are recessed radially below second sidesurfaces 561 and between opposed first side surfaces of adjoining firstprojecting portions 556. Each second projecting portion 557 is formed bytwo opposite generally coplanar base surfaces 567, which adjoin theinner extremity of opposed first side surfaces 558 and extend towardeach other, and two opposite projecting surfaces 568, which extendgenerally outwardly from axis 553 at an oblique angle from the relatedbase surface 567. Projecting surfaces 568 extend toward each other tomeet at an approximate right angle and form a third cutting edge 571.Third cutting edges 571 each have an approximate equivalent radialdimension 572 from axis 553 which is less than radial dimension 563 offirst projecting portions 556, and serve as the outer radial extremityof second projecting portions 557. As such, each third cutting edge 571is recessed radially inwardly of an imaginary straight line extendingbetween adjacent first cutting edges 562.

Cutting line 552 mounts to cutting attachments 36 and 276 insubstantially the same manner as cutting line 162. Cutting string 551operates in a manner similar to cutting string 531, but has three setsof cutting edges which are exposed sequentially as cutting line 552 isworn. First projecting portion cutting edges 562 act as initial cuttingedges and second cutting edges 566 act as secondary cutting edges.Second cutting edges 566 generally become operative after first cuttingedges 562 and cutting line 552 have been worn. Third cutting edges 571formed on projecting portion 557 act as tertiary or inner cutting edgeswhich are generally exposed after first and second cutting edges 562 and566 are worn.

Cutting strings can have embodiments with noncontinuous first projectingportions for reducing fraying of the cutting line during operation ofthe trimming device and be within the scope of the present invention. Aportion of a cutting string 581 substantially similar to cutting string531 is shown in FIGS. 27 and 28. Cutting string 581 is formed from anelongate flexible cutting line 582 extending longitudinally along acentral longitudinal axis 583 and made from a suitable material such ashigh-impact plastic. Cutting line 582 includes first and secondprojecting portions 584 and 586. First projecting portions 584 are eachformed from adjoining first and second side surfaces 587 substantiallyidentical to side surfaces 538, and second projecting portions 586 areeach formed from adjoining first and second side surfaces 588substantially identical to side surfaces 543. Side surfaces 587 and 588each extend longitudinally along cutting line 582 and generally radiallyoutwardly from longitudinal axis 583 and meet to form respective firstand second cutting edges 591 and 592.

First projecting portions 584 are provided with a plurality of generallyparallel grooves 593 spaced longitudinally along cutting line 582 andextending generally angularly about axis 583 across and through thefirst projecting portions between first and second longitudinal sidesurfaces 587 (See FIG. 28). More specifically, angular grooves 593extend perpendicularly between first and second side surfaces 587 andseparate first projecting portions 584 into cutting segments 596.Grooves 593 generally extend no deeper than the bottom of firstprojecting portions 584. In addition, the grooves are equivalentlyspaced on each first projecting portion 584 and offset with respect togrooves 593 formed on the other first projecting portions 584 so as notto substantially weaken cutting line 582. In general, only anapproximate one-half inch of the end of cutting strings are typicallyused in cutting operations. Grooves 593 can be spaced longitudinallyfrom approximately one-quarter to one and one-half inch apart.

In operation and use, grooves 593 provided on cutting line 602 canreduce fraying of the cutting line by facilitating separation of frayedcutting segments 596 from the cutting line. For example, if a firstprojecting portion 584 were to split from the balance of cutting line602 and commence fraying of the cutting line, the split, upon reachinggroove 593, would cause the frayed cutting segment 596 to separate fromthe cutting line. In this manner, further fraying would be hindered bygroove 593, the commencement of frays being more difficult than thepropagation thereof. Severing frayed cutting segments 596 also serves tobetter expose for use second cutting edges 592 on second projectingportions 586 by facilitating the separation of frayed cutting segments596.

In other embodiments of cutting strings similar to cutting strings 581,a cutting string 601 made from an elongate flexible cutting line 602extending longitudinally along a central longitudinal axis 603 isprovided (See FIG. 29). Cutting line 602 is made from a suitablematerial such as high-impact plastic, and includes first and secondprojecting portions 606 and 607 substantially identical to projectingportions 584 and 586 discussed above. More particularly, portions 606are formed from adjoining first and second side surfaces 608 which meetat first cutting edges 611 and portions 607 are formed from adjoiningfirst and second side surfaces 612 which meet at second cutting edges613.

First and second projecting portions 606 and 607 extend longitudinallyalong axis 603 in a spiral configuration. In addition, portions 606 and607 are provided with a plurality of generally annular grooves 616 whichare substantially similar to grooves 593 but extend completely aroundthe circumference of cutting line 602 through projecting portions 606and 607.

In operation and use, cutting line 602 with spiraled cutting edges 611and 613 has been found to be a more aerodynamic cutting line which isquieter in operation than cutting lines with longitudinally straightcutting edges. The spiraled configuration causes cutting string 601 toangularly rotate about axis 603 during use thereof. Such rotation alsoincreases the cutting effectiveness and life of the cutting string byavoiding concentrated cutting on any particular cutting edge 611 or 613.Grooves 616 reduce fraying in first and second projecting portions 606and 607 in the same manner as grooves 593 reduce fraying in firstprojecting portions 584.

Cutting attachments of the present invention can be formed with cuttingelements integral therewith such as cutting blades similar to thosediscussed above. A generally planar cutting attachment 626 for use witha vegetation cutting device such as trimming device 35 is shown in FIG.30. Cutting attachment 626 is formed from a thin relatively rigid body627 made of a high strength plastic and having first or top and secondor bottom generally parallel opposite surfaces 628. Body 627 includes acentral or coupling portion 631 centered on an axis of rotation 632shown in end view in FIG. 30.

Coupling means adapted to couple body 627 to trimming device 35 to causerotation about axis 632 is carried by coupling portion 631 and includesa centrally disposed hole or opening 633 in the coupling portion whichis generally circular in cross-section. Opening 633 has a pair of slots636 diametrically disposed on opposite sides of the opening which arepart of a keyway system 637 substantially identical to keyway system196. The coupling means further includes adapter assembly 198 formounting cutting attachment 626 to drive shaft 39 of trimming device 35in the manner discussed above.

A plurality of spaced apart radially extending cutting elements arecarried by body 627 for cutting vegetation as the body rotates aboutaxis 632. In this regard, body 627 includes three arms 642 integraltherewith which are symmetrically disposed about axis of rotation 632.Arms 642 have proximal and distal end portions 643 and 646 and first andsecond generally parallel opposite sides 647 which extend therebetween.Proximal end portions 643 are joined to coupling portion 631 so thatarms 642 extend radially outwardly from the coupling portion withrespect to axis 632.

Cutting elements in the form of cutting blades 651 are joined to armdistal end portions 646 and extend radially outwardly from axis 632 inlinear alignment with the related arm 642. Each cutting blade 651 issubstantially identical to cutting portion 416 of cutting blade 411discussed above, and is formed from an elongate flat planar body 652with first and second opposite cutting edges 653 and 656 extending alongthe sides thereof and first and second spaced-apart generally parallelsurfaces 657 extending between the edges in directions generallyperpendicular thereto. Cutting blade body 652 has a cross-sectionalshape substantially similar to the shape shown in FIG. 17 and has aplurality of parallel vee-shaped indentations 658 formed on each surface657 and a plurality of spaced-apart parallel reinforcing portions orribs 661 extending generally transversely of cutting edges 653 and 656on each surface 657. Indentations 658 serve to partition cutting bladebody 652 into a plurality of knife elements 662.

Arms 642 are each formed with a yieldable portion or flex sectionbetween proximal and distal end portions 643 and 646 created by twospaced-apart parallel slots 663 which extend through surfaces 628 andare longitudinally aligned with sides 647. Slots 663 form two oppositeouter and one central narrow support portions 666 in each arm 642, witheach central support portion 666 having aligned and opposite facingbumps 667 formed thereon and extending into slots 663 on either sidethereof.

In operation and use, cutting attachment 626 with cutting blades 651thereon is mounted on trimming device 35 in substantially the samemanner as cutting attachments 36 and 276. Cutting blades 651 operate insubstantially the same manner as cutting blades 411. Slots and supportportions 663 and 666 permit arm distal end portions 646 and cuttingblades 651 mounted thereon to move relative to arm proximal end portion643 in a plane defined by first and second sides 647 when an object isencountered by the cutting blades. More particularly, slots 663 permitnarrow support portions 666 to pivot in alignment with respect toproximal end portion 643. The narrow configuration of support portions666 permit arms 642 and cutting blades 651 to absorb a considerableamount of the damaging shock forces experienced by the cutting blades onsuch an impact. The engagement of bumps 667 with the two outer supportportions 666 limit this pivotal movement so as to avoid structurallydamaging bending of arms 642.

The cutting attachments of the present invention can be adapted for usewith cutting devices other than trimming devices, such as lawn mowers,edgers and leaf shredders, and be within the scope of the presentinvention. More specifically, the cutting attachments can be used withconventional lawn mowers, not shown in the drawings, having elongateblades rotating about an axis substantially perpendicular to the ground.For this purpose, a cutting attachment 671 formed from a thin elongaterelatively rigid body 672 is provided (See FIGS. 31 and 32). Cuttingattachment body 672 is made of a high strength plastic and has first ortop and second or bottom generally parallel opposite surfaces 673. Body672 includes a central or coupling portion 676 centered on an axis ofrotation 677.

Coupling means adapted to couple body 672 to a lawn mower to causerotation about axis 677 is carried by coupling portion 676 and includesa centrally disposed hole or opening 678 in the coupling portion whichis generally circular in cross-section. Opening 678 has a pair of slots681 diametrically disposed on opposite sides of the opening which arepart of a keyway system 682 substantially identical to keyway system196. Cutting attachment 671 can carry other coupling means for rotatablycoupling it to a lawn mower in a manner known to those skilled in theart and be within the scope of the present invention.

A plurality of spaced apart radially extending cutting elements arecarried by body 672 for cutting vegetation as the body rotates aboutaxis 677. In this regard, body 672 includes two arms 683 integraltherewith which are diametrically opposed about axis of rotation 677.Arms 683 have proximal and distal end portions 686 and 687 and first andsecond generally parallel opposite sides 688 which extend therebetween.Proximal end portions 686 are joined to coupling portion 676 so thatarms 683 extend radially outwardly from the coupling portion withrespect to axis 677.

Cutting elements in the form of cutting blades 411 shown in FIG. 16 arejoined to arm distal end portions 687 and extend radially outwardly fromaxis 632. Means for pivotly mounting and coupling each cutting blade 411to distal end portion 687 includes a bolt 691 which extends through bore418 in cutting blade 411 and a bore 692 extending through surfaces 673of the distal end portion. A nut 693 is threadedly connected to the endof bolt 691 for securing it within bores 418 and 692.

Although mounted to a lawn mower instead of a cutting device such astrimming device 35, cutting attachment 671 operates in substantially thesame manner as cutting attachment 626. Cutting blade 411 operates insubstantially the same manner when mounted to cutting attachment 671 aswhen mounted to cutting attachment 36 or 276 as discussed above.

A cutting attachment adapted for use with a lawn mower can have otherconfigurations and be within the scope of the present invention. Anotherembodiment of such a cutting attachment is illustrated in FIGS. 33 and34 where a cutting attachment 701 similar to cutting attachment 671 isshown. Cutting attachment 701 is formed from a thin elongate relativelyrigid body 702 made of a high strength plastic and having top and bottomgenerally parallel opposite surfaces 703 and a coupling portion 706centered on an axis of rotation 707 shown in end view in FIG. 33.Coupling means adapted to couple body 702 to a lawn mower to causerotation about axis 707 includes a centrally disposed opening 708 in thecoupling portion which has a pair of slots 711 diametrically disposed onthe opposite sides thereof. Slots 711 are part of a keyway system 712substantially identical to keyway system 196.

Cutting attachment body 702 includes two arms 713 integral therewithwhich are diametrically opposed about axis of rotation 707. Arms 713have proximal and distal end portions 716 and 717 and first and secondgenerally parallel opposite sides 718 which extend therebetween.Proximal end portions 716 are joined to coupling portion 706 so thatarms 713 extend radially outwardly from the coupling portion withrespect to axis 707. Arms 713 are each formed with a yieldable portionbetween proximal and distal end portions 716 and 717 created by twospaced-apart parallel slots 721 which extend through surfaces 703 andare longitudinally aligned with sides 718. Slots 721 form two oppositeouter and one central narrow support portions 722 in each arm 713, witheach central support portion 722 having aligned and opposite facingbumps 723 formed thereon and extending into slots 721 on either sidethereof.

Cutting elements in the form of cutting blades 731 are joined at obliqueangles to arm distal end portions 717 and extend outwardly from axis707. Each cutting blade 731 is substantially identical to the cuttingportion of cutting blade 436 discussed above, and is formed from anelongate flat planar body 732 with first or leading and second ortrailing opposite cutting edges 733 and 736 extending along the sidesthereof and first and second spaced-apart generally parallel surfaces737 extending between the edges in directions generally perpendicularthereto. Edges 733 and 736 are inclined with respect to the respectivearm 713 away from the direction of travel of cutting attachment 701.Cutting blade body 732 has a cross-sectional shape substantially similarto the shape shown in FIG. 17 and has a plurality of parallel vee-shapedindentations 738 formed on one surface 737 thereof and a plurality ofspaced-apart parallel reinforcing portions or ribs 741 extendinggenerally transversely of cutting edges 733 and 736 on said surface 737.Indentations 738 serve to partition cutting blade body 732 into aplurality of knife elements 742. Cutting blade body 732 has a thin finor airlift 743 mounted to trailing edge 736 near the end thereof,airlift 743 being mounted at an oblique angle to surfaces 737 andextending generally upwardly therefrom.

Cutting attachment 701 operates on a lawn mower in substantially thesame manner as cutting attachment 626 operates on trimming device 35.Inclined cutting blades 731 thereon serve a similar function as cuttingblade 476 discussed above. Aerodynamic airlift 743, known to thoseskilled in the art, assists in keeping cutting blades 731 close to theground.

Adapter assembly 198 can have other configurations and be within thescope of the present invention. For example, a sleeve element 751 can beprovided which is substantially identical to sleeve element 201 and hasa lower end portion 752 with an end 753 (See FIG. 37). Sleeve element751 is provided with a centrally disposed bore 756 which extendslongitudinally therethrough and opens into a recess or receptacle 757provided in end 753. Bore 756 is adapted to snugly receive drive shaft39 and is so configured and dimensioned. Receptacle 757 is formed by aplanar stop surface 758 which is generally parallel with end 753, aninner surface 761 which generally perpendicularly adjoins stop surface758 and extends toward end 753, a shoulder 762 which generallyperpendicularly adjoins inner surface 761 and is generally parallel withend 753, and an inner surface 763 which generally perpendicularlyadjoins and interconnects shoulder and end 762 and 753.

Receptacle 757 has upper and lower portions 757a and 757b. Upper portion757a is generally formed by stop and inner surfaces 758 and 761, withinner surface 761 being cross-sectionally configured and dimensioned tonon-rotatably receive a hexagonal securement bolt head. Lower portion757b is generally formed by shoulder and inner surface 762 and 763, withinner surface 763 being cross-sectionally configured and dimensioned tonon-rotatably receive a larger bolt head than that received by upperportion inner surface 761.

In operation and use, adapter assembly 198 with sleeve element 751permits the adapter assembly and the cutting attachments describedherein to be easily used with trimming devices 35 having securementbolts with varying head sizes. Sleeve element 751 can be simply adaptedto accommodate additional bolt head sizes by utilizing a bolt adaptermeans therewith similar to socket 225 discussed above.

In another embodiment of a cutting or trimmer line having renewableedges for use on a rotating string trimmer, a cutting or trimmer string801 formed from an elongate flexible cutting line 802 is provided (seeFIG. 38). Cutting line 802 is made by any suitable means such asextrusion from a suitable material such as high-impact plastic and has acentral longitudinal axis 803 shown in end view in FIG. 38. Trimmerstring 801 is generally star-shaped in cross-section and has five sets806 of outer cutting edges spaced circumferentially about axis 803 atapproximately equivalent intervals of 72°. Each set 806 of outer edgesincludes first and second outermost cutting portions or elements 807formed with sharp cutting edges 808 at the radial extremities thereof.Cutting elements 807 each have an approximately equivalent radialdimension equal to the distance between respective edge 808 and axis803. Sets 806 also include a third cutting portion or element 812disposed in a recess 813 formed between outermost cutting elements 807.Third or inner cutting elements 812 are each formed with a sharp edge814 and each have a radial dimension 816 less than radial dimensions811.

Trimmer string 801 further includes five innermost cutting portions orelements 820 spaced circumferentially about axis 803 at approximatelyequivalent intervals of 72°. Each innermost cutting element 820 isdisposed in a recess 821 formed between each set 806 of outer edges.Cutting elements 820 are each formed with a cutting edge 822 at theradial extremity thereof and each have a radial dimension 823 less thanradial dimensions 811 and 816.

The equivalent spacing about axis 803 of cutting elements 807, 812, and820 serves to balance trimmer string 801 during use. Although thecutting elements formed in cutting line 802 are shown as being generallytriangular in cross section, it should be appreciated that these cuttingelements can have other configurations and be within the scope of thepresent invention.

In operation and use, the pronounced sets 806 of outer edges formed oncutting line 802 serve as initial cutting edges. After outermost cuttingelements 807 have been worn, inner cutting elements 812 therebetween areexposed and serve as fresh cutting edges. Further use of cutting string801 causes cutting elements 807 and 812 to wear radially inwardly sothat cutting edge 822 of innermost cutting elements 820 are exposed andserve as yet an additional fresh set of cutting edges.

A cross-sectional view of another embodiment of the string trimmer lineof the present invention is illustrated in FIG. 39. cutting or trimmerstring 831 shown therein is formed from an elongate flexible cuttingline 832 made from a suitable material such as high-impact plastic andhas a central longitudinal axis 833. cutting string 831 is generallyX-shaped in cross-section and has four outer projecting portions 836which extend substantially continuously along the length of cutting line832 and are circumferentially-spaced about axis 833 thereof atapproximately equivalent intervals of 90°. Each projecting portion 836extends radially outwardly from axis 833 and is generally square incross-sectional shape.

More specifically, projecting portions 836 are provided with first andsecond spaced-apart outermost cutting portions or elements 837 formed inpart by corners 838 of projecting portions 836 and having opposedcorners or edges 841 formed by a recess 842 provided in the center ofthe radial extremity thereof. Corners 838 and edges 841 can each serveas cutting edges and have respective radial dimensions 843 and 844 asshown in FIG. 39. Radial dimension 843 of cutting edge 838 is slightlylarger than radial dimension 844 of cutting edge 841 and, as a result,cutting edges 838 are the outermost cutting edges of trimmer string 831.It should be appreciated that each cutting element 837, with cuttingedges 838 and 841 thereof, can be viewed as a single cutting edge and bewithin the scope of the present invention.

Each projecting portion 836 is provided with a cutting portion orelement 847 disposed in the center of recess 842 between cuttingelements 837. Cutting elements 847 are each formed with a cutting edge848 at the radial extremity thereof and have a radial dimension 851which is less than radial dimensions 843 and 844.

Cutting string 831 further includes four innermost cutting portions orelements 852 which are circumferentially spaced about axis 833 atapproximately equivalent intervals of 90°. In this manner, a cuttingelement 852 is disposed between each projecting portion 836 in a recess853 therebetween. Cutting elements 852 are each generally triangular incross-sectional shape and have a cutting edge 854 at the radialextremity thereof and a radial dimension 855 which is less than radialdimensions 843, 844 and 851.

As can be seen, cutting string 831 has four sets of cutting edges forgenerally sequentially engaging the vegetation being trimmed as thecutting string wears. Each set of cutting edges consists of four cuttingedges and the cutting edges of each sequential set have a radialdimension less than the cutting edges of the previous sequential set ofcutting edges.

In operation and use, the relatively massive projecting portions 836 ofcutting string 831 can serve as radially outer cutting edges, with edges838, 841 and 848 serving to sequentially provide the cutting portionswith a sharp cutting edge. Innermost cutting edges 854 are exposed onceprojecting portions 836 have worn to a radial dimension whichapproximates radial dimension 851 of innermost cutting elements 852.

Yet another embodiment of the trimmer line of the present invention isillustrated in FIG. 40 which shows a cutting or trimmer string 861formed from an elongate flexible cutting line 862 made from a suitablematerial such as high-impact plastic and having a central longitudinalaxis 863. Trimmer string 861 is generally triangular in cross-sectionalshape, being formed with at least two sets or clusters of outer cuttingedges, and as shown in FIG. 43 three clusters 866 of outer cuttingedges, spaced circumferentially about axis 863 at approximatelyequivalent intervals of 120°. Each cluster 866 includes first and secondoutermost cutting portions or elements 867 formed substantiallytriangular in cross-sectional shape with sharp cutting edges 868 at theradial extremities thereof. Cutting elements 867 each have anapproximately equivalent radial dimension 871. Clusters 866 furtherinclude a third cutting portion or element 872 disposed in a recess 873formed between outermost cutting elements 867. Third or inner cuttingelements 872 are each formed substantially triangular in cross-sectionalshape with a sharp edge 876 and each have a radial dimension 877 lessthan radial dimension 871.

Outwardly projecting clusters 866 form a recess 881 between each clusterand trimmer string 861 is further provided with at least two clusters ofinner cutting edges, and as shown in FIG. 40 three clusters 882 of innercutting edges in recesses 881. More specifically, clusters 882 arespaced circumferentially about axis 863 at approximately equivalentintervals of 120°, a cluster 882 disposed in each recess 881 betweenadjacent clusters 866.

Each cluster 882 has a shape which generally approximates a truncatedtriangle and is formed with first and second spaced apart cuttingportions or elements 886 formed substantially triangular incross-sectional shape with sharp cutting edges 887 at the radialextremities thereof. Cutting elements 886 each have an approximatelyequivalent radial dimension 888 which is less than radial dimensions 871and 877. Clusters 882 each further include a third or innermost cuttingportion or element 891 disposed in a recess 892 formed between cuttingelements 886. Innermost cutting elements 891 are each formedsubstantially triangular in cross-sectional shape with a sharp edge 893and each have a radial dimension 896 less than radial dimension 888.

In operation and use, trimmer string 861 has inner and outer clusters866 and 882 of cutting edges for extending the cutting life thereof. Asseen above, each cluster 866 is initially provided with two cuttingportions or edges 868 so that trimmer string 861 has six initial cuttingedges. As these six cutting edges are worn away, a third cutting element872 in cluster 866 is exposed to provide a fresh cutting edge. Furtherwear of trimmer string 861 exposes inner clusters 882 which are alsoprovided with an aggregate of six initial cutting elements 886.Following wear of cutting elements 886, the three innermost cuttingelements 891 are exposed so as to further extend the cutting life oftrimmer string 861. As can be seen, trimmer string 861 is provided withfour sets of cutting edges which are exposed sequentially to provide acutting string with a significant working life.

Yet another embodiment of a cutting or trimmer line having renewableedges is illustrated in FIG. 41. Cutting or trimmer string 901 showntherein is formed from an elongate flexible cutting line 902 made from asuitable material such as high-impact plastic and has a centrallongitudinal axis 903. Cutting string 901 is generally triangular incross-section and is provided with clusters 906 of outer cutting edgessubstantially identical to outer clusters 866 of trimmer string 861.Briefly, clusters 906 have first and second spaced apart outermostcutting portions or elements 907 formed substantially triangular incross-sectional shape with sharp cutting edges 908 at the radialextremities thereof. Cutting elements 907 each have an approximatelyequivalent outermost radial dimension 911. Clusters 906 further includea recess 912 formed in part by cutting elements 907 and are providedwith a third or inner cutting portion or element 913 therein. Theseinner cutting elements 913 are each formed substantially triangular incross-section with a sharp edge 916 and each have an outermost radialdimension 917 less than radial dimension 911 of cutting elements 907. Arecess 918 is provided between each cluster 906. The significantseparation between each cluster 906 provided on cutting string 901facilitates its manufacture.

In operation and use, cutting string 901 is provided with six initialcutting edges 908. After these cutting edges are worn away, innercutting edges 916 are exposed to further extend the life of cuttingstring 901.

Although the cutting strings described in this application are describedfor use with conventional rotating string trimmers, these cuttingstrings can be used with other vegetation cutting devices such aslawnmowers and be within the scope of the present invention.

Another cutting attachment 921 of the present invention is illustratedin FIG. 42. Cutting attachment 921 is substantially similar to cuttingattachments 36 and 276 described above and is designed as a basic unitfor use with cutting blades only. Cutting attachment 921 has a centralwall portion 922 substantially similar to central wall portion 281 ofcutting attachment 276 and an outer wall portion 923 substantiallysimilar to outer wall portion 47 of cutting attachment 36. Outer wallportion 923 has a lower surface (not shown) substantially similar to thelower surface of outer wall portion 47, but does not include an annularridge similar to annular ridge 88 of cutting attachment 36.

Central and outer wall portions 922 and 923 form an outer cavity 926which has a plurality of ribs, and as shown in FIG. 42 three radiallyextending ribs 927, which extend between the central and outer wallportions. Ribs 927 are each provided with two radially extendingrecesses 928 therein for reducing the weight and mass thereof. In thismanner, each rib 927 consists of three rib portions 927a. Ribs 927 eachfurther include a boss portion 931 adjacent outer wall portion 923 whichhas a bore 932 extending therethrough for permitting a cutting blade tobe attached to cutting attachment 921.

Another embodiment of a cutting element is shown in FIG. 43 in which acutting blade 941 substantially similar to cutting blades describedabove is provided. Cutting blade 941 is formed from an elongate flatplanar body of a high-impact plastic having mounting and cuttingportions 942 and 943. Cutting portion 943 includes first and secondspaced apart generally parallel surfaces 946 extending between oppositecutting edges 947 and a rounded end in the form of a cutting edge 948which adjoins edges 947. Edges 947 and 948 are each formed with U shapedserrations 951 therein which form teeth 952. Serrations and teeth 951and 952 enhance the cutting action of cutting blade 941.

Another cutting blade 961 of the present invention is shown in FIG. 44.Cutting blade 961 is substantially similar to cutting blade 941 exceptthat cutting portion 962 thereof tapers as it extends outwardly frommounting portion 963. Cutting portion 962 has opposite first and secondgenerally parallel surfaces 966 which extend between opposite cuttingedges 967. Cutting edges 967 taper toward each other and each adjoin arounded end in the form of end cutting edge 968. Edges 967 and 968 areeach formed with U shaped serrations 971 separated by cutting teeth 972.Cutting blade 961 operates in substantially the same manner as cuttingblade 941.

It is apparent from the foregoing that a new and improved cuttingattachment which has a unitary lightweight body with a self-cleaningshape has been provided. The cavities therein are formed from generallysmooth and outwardly inclined surfaces to inhibit weeds from becomingcaught therein. In addition, the cutting attachment has a skid plate anda cover plate accessory can be mounted thereon. The cutting attachmentcan be readily coupled to various types of cutting devices.

Improved cutting elements in the form of cutting blades and cuttingstrings are provided for use with the cutting attachment. In oneembodiment, a cutting blade is provided with an inner cutting edge whichcan be exposed for use after the outermost leading cutting edge hasworn. In other embodiments, cutting blades are provided with serratedcutting edges and aerodynamic configurations. An improved structure isprovided for yieldably mounting cutting blades to a cutting attachment.

A cutting string is provided which does not cause significant wear tothe cutting attachment and which includes an inner cutting edge for useafter the outermost cutting edge has worn. In other embodiments, cuttingstrings are provided which inhibit fraying thereof and which areaerodynamically spiraled in longitudinal configuration.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,and to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A cutting string for use with a cuttingattachment rotatably mounted to a cutting device to cut vegetationcomprising a flexible cutting line with a central longitudinal axis, thecutting line having at least three substantially continuous firstprojecting portions extending longitudinally along the cutting line andspaced circumferentially from each other and at least threesubstantially continuous second projecting portions extendinglongitudinally along the cutting line and spaced circumferentially fromeach other, the first and second cutting portions having respectiveradial extremities, each second projecting portion spaced between twoadjacent first projecting portions, the radial extremity of each secondprojecting portion being recessed radially inwardly of an imaginarystraight line extending between the radial extremities of adjacent firstprojecting portions so that as adjacent first projecting portions becomeworn the second projecting portion therebetween is exposed to cutvegetation.
 2. A cutting string as in claim 1 wherein the radialextremities of the first projecting portions are cutting edges.
 3. Acutting string as in claim 1 wherein the radial extremities of the firstprojecting portions have radial dimensions with respect to the centrallongitudinal axis which are equal.
 4. A cutting string as in claim 3wherein the radial extremities of the second projecting portions haveradial dimensions with respect to the central longitudinal axis whichare equal.
 5. A trimmer line for use with a rotating string trimmer tocut vegetation comprising an elongate flexible cutting element extendingalong a longitudinal axis and having first and second radially extendingcutting portions which extend longitudinally of the axis and are spacedcircumferentially from each other, the second cutting portion beingrecessed radially inwardly of the first cutting portion so that when thefirst cutting portion becomes worn the second cutting portion becomesfurther exposed to cut vegetation.
 6. A trimmer line as in claim 5wherein the elongate flexible cutting element is made from plastic.
 7. Atrimmer line for a string trimmer comprising an elongate flexiblecutting element having a longitudinal axis, the cutting element havingtwo radially-extending circumferentially spaced-apart first cuttingportions extending longitudinally of the axis and a radially-extendingsecond cutting portion extending longitudinally of the axis, the firstand second cutting portions having respective radial extremities, thesecond cutting portion being interposed between the first cuttingportions, the radial extremity of the second cutting portion beingrecessed radially inwardly of the radial extremities of the firstcutting portions so that when the radial extremity of the first cuttingportions become worn the radial extremity of the second cutting portionbecomes further exposed to cut vegetation.
 8. A trimmer line as in claim7 wherein the elongate flexible cutting element has threeradially-extending circumferentially spaced-apart first cutting portionsand three radially-extending circumferentially spaced-apart secondcutting portions, each of the second cutting portions being interposedbetween adjacent first cutting portions and the radial extremities ofeach of the second cutting portions being recessed radially inwardly ofthe radial extremities of adjacent first cutting portions.
 9. A trimmerline as in claim 7 wherein the cutting element is made from plastic. 10.A trimmer line as in claim 7 wherein the radial extremity of the secondcutting portion is tapered to form a sharp cutting edge.
 11. A trimmerline as in claim 10 wherein the radial extremity of each of the firstcutting portions is tapered to form a sharp cutting edge.
 12. A trimmerline as in claim 7 wherein the elongate flexible cutting element hasfour radially-extending circumferentially spaced-apart first cuttingportions and four radially-extending circumferentially spaced-apartsecond cutting portions, each of the second cutting portions beinginterposed between adjacent first cutting portions and the radialextremities of each of the second cutting portions being recessedradially inwardly of the radial extremities of adjacent first cuttingportions.
 13. A trimmer line for a string trimmer comprising an elongateflexible cutting element having a longitudinal axis, the cutting elementhaving two radially-extending circumferentially spaced-apart firstcutting portions extending longitudinally of the axis and aradially-extending second cutting portion extending longitudinally ofthe axis, the first and second cutting portions having respective radialextremities, the second cutting portion being interposed between thefirst cutting portions, the radial extremity of the second cuttingportion being recessed radially inwardly of an imaginary straight lineextending between the radial extremities of the first cutting portionsso that when the radial extremity of the first cutting portions becomeworn the radial extremity of the second cutting portion becomes exposedto provide a new cutting portion for the line.
 14. A trimmer line as inclaim 13 wherein the elongate flexible cutting element has threeradially-extending circumferentially spaced-apart first cutting portionsand three radially-extending circumferentially spaced-apart secondcutting portions, each of the second cutting portions being interposedbetween adjacent first cutting portions and being recessed radiallyinwardly of an imaginary straight line extending between the radialextremities of adjacent first cutting portions.
 15. A trimmer line as inclaim 13 wherein the radial extremity of the second cutting portion istapered to form a sharp cutting edge.
 16. A trimmer line as in claim 15wherein the radial extremity of at least certain of the first cuttingportions are tapered to form sharp cutting edges.
 17. A trimmer line asin claim 13 wherein the elongate flexible cutting element has fourradially-extending circumferentially spaced-apart first cutting portionsand four radially-extending circumferentially spaced-apart secondcutting portions, each of the second cutting portions being interposedbetween adjacent first cutting portions and being recessed radiallyinwardly of an imaginary straight line extending between the radialextremities of adjacent first cutting portions.